LONDON, May 30 (Reuters) - A force majeure has been declaredon the Usan grade of Nigerian crude oil, traders said onThursday, adding to the problems facing Africa's largest oilexporter.
A trader said that production was completely halted, andthat more information about the reason behind the force majeurewould be made available after the weekend.
Total which operates the Usan field wasunavailable for comment.
Four cargoes of Usan representing around 127,000 barrels perday of Usan were due to be exported in June.
The force majeure for Usan adds to those on Royal DutchShell's Bonny Light and Eni's Brass river.
Shell declared a force majeure on Bonny Light on March 5because of "unprecedented" levels of theft.
Shell said on Thursday the force majeure - a declarationthat exempts parties to a contract from their obligations due tocircumstances beyond their control - is still in place.
Analysts say that the unreliability of supply is encouragingbuyers to look elsewhere for more steady streams of oil.
